Take control of, or fast travel to the Washington Monument Control Point. Once there, go into the supply area. You’ll see a small blue button with a tv just above. After 7 pm in game time, interact with this. The T.V. will light up, showing the locations of three graves. The graves can be found as follows
1- 1147 N / 2591 W, just outside the flooded levee control point facing the toppled shipping containers.
2- 1104 N / 3009 W looking towards the supplies on the monument.
3- 948 N / 2863 W looking at the side of the memorial that says “UNITE”.
Salute each grave in turn and in no particular order. Once all 3 have been Saluted, return to the supply room in the memorial. Interact with the button once again. The T.V. this time should light up with the orange Division ring. Exit and find the red circle of light outside the monument. The hunter will spawn for the final mask.